1. Technical Field
The present invention relates to an infrared absorbing composition, and to an infrared absorbing ink, a recorded article, an image recording method, and an image detecting method using the same.
2. Description of Related Art
Near-infrared absorbing coloring materials which do not substantially absorb visible light but absorb infrared light have been widely used for various kinds of optoelectronics products such as near-infrared absorbing filters.
As in a security-related devices such as those for text or image validation, for example, the optoelectronics products may be exposed to high temperature, high humidity, or light irradiation depending on the use pattern, such as outdoor use. For such reasons, it is important that the near-infrared absorbing coloring materials used remain stable over a long period of time, and it is required that the near infrared absorbing coloring materials are stable so that performance deterioration such as degradation over time is unlikely to occur. In particular, it is essential for the coloring material itself to have resistance to light to maintain high product quality for a long period of time.
With regard to technology related to the above, a naphthalocyanine near-infrared absorbing agent or an alkyl phthalocyanine near-infrared absorbing agent having a specific structure is proposed as a near-infrared absorbing agent having excellent light resistance, weather resistance, and heat resistance (for example, see Japanese Patent Application Laid-Open (JP-A) No. 2-43269 and JP-A No. 2-138382).
As a near-infrared absorbing ink which exhibits almost no absorption of visible light, a near-infrared absorbing ink having excellent light resistance due to containing a specific naphthalocyanine compound is disclosed (for example, see, JP-A No. 3-79683).